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Two 6" Telescopes from Orion - Fast Newt vs. Slow MCT. Orion SVD 6" Newt meets the Orion Argonaut 150 MCT
These two instruments have little in common aside from aperture. They are designed for decidedly different markets and this is certainly reflected in their decidedly different prices and supplied accessories. The SVD 6" Newt is configured as a complete package. It is not really necessary to buy any accessories in order to start observing. In rather sharp contrast to this approach, the Argonaut 150 is essentially an OTA and finder scope. This is a common approach for higher end telescopes. The assumption is that this higher quality instrument will be purchased by more experienced observers who already own eyepieces, star diagonals and the like.
Both telescopes are offered by Orion (USA) with the Skyview Deluxe (SVD) Equatorial (EQ) mount although the Argonaut 150 is available without a mount as an Optical Tube Assembly (OTA). We'll take a look at the adequacy of the SVD mount when used with each instrument.
Given the above cited differences, it is probably prudent to look at these instruments within the context of their respective markets.
Orion Skyview Deluxe (SVD) 6" Newtonian Reflector
Fit and Finish: Good. Very attractive glossy black finish. All components seem to fit nicely. The overall
design is sound and competently implemented.
Optics: Good. Like all fast Newtonian reflectors, the 6" SVD does display some coma at the edge of field. Although the coma is easily detected, I've never found it to be distracting. Assuming the scope is for visual use only, the coma is not a serious issue. On balance, I found the optics to be surprisingly good.
Collimation - Collimation can be a real adventure for the uninitiated. The proper alignment of the optical components in a fast (f/5 or less) Newtonian reflector is critical for good performance. The exact steps necessary to achieve good collimation are conveniently ignored in the advertisements for fast Newts. Nothing to it? If you are a beginner, there is plenty to it.
The primary mirror has to be removed and a dot or spot placed dead center in the middle of the mirror. Many beginners will find this to be an intimidating experience. An accurate collimating tool is also required. I've used two different collimation tools with the SVD 6" Newt.
- The Orion Collimating Eyepiece. The Orion tool is a combination sight tube and Cheshire eyepiece. It is probably fine for slower (f/6 or more) Newtonian reflectors but is not sufficiently accurate for a f/5 instrument. The barrel of the Orion product seems a bit undersized and this certainly seems to compromise the accuracy of the device. The accuracy can be improved noticeably by wrapping some thin tape around the barrel. A footnote in the present Orion catalog recommends the Orion Lasermate Collimator for f/5 or faster Newts. Probably a good idea.
- Tectron Collimation Tools. The Tectron Tools may be purchased individually or as a complete set. The complete sets includes, a Sight Tube, Cheshire Eyepiece, Autocollimator and a booklet entitled "New Perspectives in Collimation" by Vic Menard and Tippy D'Auria. The booklet is extremely worthwhile and may be purchased separately for about $8.00. I was able to achieve very good collimation without the use of the Autocollimator.
Supplied Eyepieces - Two generic plossls (25mm and 9mm) are furnished. The 25mm is a pretty decent eyepiece, certainly better than most of the Kellner's commonly supplied with instruments in this price range. The 9mm seems a bit less sharp but it is certainly acceptable.
Finder Scope - Plastic tube. The 6x30 finder scope is not exactly a work of art but I have seen far worse. It is really limited more by aperture than by quality. An 8x50 would certainly be better but is probably more trouble than it is worth for a 6 inch telescope with such a wide field of view.
Focuser - The 1 ¼" rack and pinion focuser has a metal mechanism with plastic focusing knobs. It is quite smooth in operation. More than adequate for the task.
Ergonomics - The supplied tube rings could be more appropriately described as tube clamps. The OTA is not easily rotated. It is usually necessary to undo the clamps, lift the OTA from the rings, rotate it to the desired position and clamp it down in that position. This is not as awkward as it may sound but it does require a little practice to confidently execute this maneuver in the dark. The need to occasionally rotate the OTA is a given with any EQ mounted Newtonian reflector if one wishes to have the eyepiece is a position that permits comfortable viewing.
Orion Argonaut 150 MCT
Made in Russia, the Argonaut is actually the Intes MK67. The only difference is the color of the OTA (black for Orion, white for Intes). A thorough review of the Argonaut 150 MCT (and Mak-Newt) was published in Sky & Telescope. This review is available the Sky Publishing web site - www.skypub.com. I'll attempt to touch on some issues which were not addressed in the Sky & Telescope review, specifically, the adequacy of the Skyview Deluxe Equatorial mount.
Fit and Finish: Very Good. The appearance of the OTA is utilitarian. The flat black finish is very well applied and durable. All components seem well machined and carefully fitted.
Optics: Very Good. Contrast is high and reminiscent of the image attainable in 3 or 4 inch apochromatic refractors. The standard claim is that the contrast is as good as a 4 inch apo. This strikes me as being something of a reach, but it is certainly in the neighborhood.
Collimation: I checked the collimation upon receipt and it was right on the money. A year later, the collimation is unchanged.
Supplied Eyepieces - None. Since this is not generally considered to be an instrument for beginners, most purchasers will already own eyepieces or diagonals. A nice starter set for the Argonaut 105 would be a 32mm plossl for 60x (about $60.00), a 20mm plossl for 90x (about $50.00) and a 2x Barlow ($25-$40).
Finder Scope - 7x35. Very sturdily constructed. Metal tube. May be focused by rotating the eyepiece. Crosshairs are a bit thick but do not meet in the center thereby enabling the user to have a clear view of objects that are centered. Non-illuminated but there is a threaded plug in the side of the unit which accepts an illuminator. It is certainly better than the ubiquitous 6x30 devices found on less expensive instruments. Intes employs a rather unique non-dovetail system for attaching the finder scope to the OTA and it works quite nicely. The finder scope is held in place by a single, large knurled metal knob and it holds alignment very well. A little more aperture would make a big difference but it is a pretty good piece of gear and upgrading it is not an absolute necessity.
Focuser - A Crayford-type 2 inch drawtube which is very smooth in operation. An adapter (not included) is required in order to use 1 ¼" eyepieces as they will not come to focus in a 2" diagonal. Heavy eyepieces can frustrate the focuser but the tension on the drawtube is easily adjusted. There is also a focuser lock. Like most features on the Argonaut, the emphasis is on function rather than esthetics. There is no image shift or backlash.
Ergonomics - Since the Argonaut uses the same type of star diagonal found in refractors, adjustment of the viewing angle is rather easy. Simply rotating the diagonal will place the eyepiece in the desired position. It is possible to rotate the entire focuser on the Argonaut but it requires the use of a tiny Allen wrench. A great project for fumbling around in the dark and losing things.
|Argonaut 150||6” SVD Reflector|
|Country of Origin||Russia||Taiwan|
|Focuser||Crayford-Type||Rack & Pinion|
|Drawtube Size||2”||1 ¼”|
|Length||14 inches||27 inches|
|Weight||9.5 lb.||11 lb.|
|Price of Optical Tube Assembly (OTA)||$899.00||Not Available as an OTA|
|Price with SVD EQ Mount||$1,099.00||$499.00|
Yes – Cordura
|25mm & 9mm plossls
2”-1 ¼” Eyepiece Adapter
|1 ¼” Mirror Star Diagonal
Recommended Accessories *
1x Red Dot Finder
|Tectron Sight Tube||$29.00||$29.00|
|Tectron Cheshire Eyepiece||$38.00||$38.00|
|“Perspectives on Collimation” Booklet||$8.00||$8.00|
* Recommended Accessory Notes:
1x Red Dot Finder – the Celestron Star Pointer is widely available for $25.00
2x Barlow – The 2x GTO Barlow from Hands on Optics is an excellent choice for about $25.00.
Tectron Sight Tube, Cheshire eyepiece & “Perspectives …” booklet – See discussion under Collimation for the 6” SVD Reflector.
Dew or Light Shield: A dewshield (not included) is a practical necessity. The Flexishield sold by Orion works well.
Eyepiece Compatibility: Orion notes in their catalog that 1 ¼" eyepieces will not come to
focus when used with a 2" diagonal and 2" to 1 ¼" adapter. This appears to be true. Eyepieces
that are 1 ¼" in diameter require the use a 2" to 1 ¼" adapter and 1 ¼"
diagonal. The following 1 ¼"
eyepieces all came to focus.
32mm Orion Sirius plossl, 30mm Celestron Ultima, 28mm RKE, 26mm Orion Sirius plossl, 25mm Orion Ultrascopic, 25mm GTO plossl, 22mm Vixen SW, 20mm GTO-MC plossl, 18mm Celestron Ultima, 17mm Orion Sirius Plossl, 15mm Orion Ultrascopic, 14mm Orion LV, 9mm Vixen LV, 7mm Pentax XL, 6mm Vixen LV.
6" Newtonian Skyview Deluxe (SVD) Equatorial Mount
More than adequate for this instrument. I have found that, over time, there is a tendency for some slack to develop in the declination axis. The most obvious symptom is that the mounting plate seems to loosen up. The worm gear that moves the mount in Declination is attached by two fairly substantial hex bolts. Removing this small component ( quite easy) and reattaching it seems to eliminate the problem for a substantial period of time. It could be that torquing the hex bolts down more vigorously would effect a more permanent solution but I have been reluctant to adopt this approach.
A non-illuminated polar alignment scope is included with the SVD and seems to work quite well. For casual visual use, it is not necessary to use the polar alignment scope. Pointing the mount in the general direction of Polaris is usually more than adequate.
Argonaut 150 MCT Skyview Deluxe (SVD) Equatorial Mount
There are, potentially, two methods which may be employed for attaching the OTA to the SVD.
Tube Rings - Not the worst idea I've ever had, but close. My small thought was to gain better control of balancing
the OTA in the Declination axis. Unfortunately, the OTA is so short that it is impossible to move it far enough
forward to achieve the desired balance. The tube rings add weight and mass but provide no benefit.
¼"-20 Adapter - Certainly better than the tube ring approach. The adapter supplied by Orion is designed to attach to the pair of ¼" hole in the base plate of the OTA. A better idea, to be sure, but it is still tough to balance on the declination axis.
For use with the Argonaut 150 MCT, The SVD is acceptable but not entirely desirable.
Vixen Custom D Altaz or Vixen Great Polaris EQ Mount
It's a bit unusual to lump an altaz and EQ mount together, but in this particular case, the primary issue (balance) is the much the same since both Vixen products employ the identical dovetail mounting system. As a consequence, the two methods for affixing the Argonaut to either mount are the same - tube rings or a ¼"-20 adapter. Neither approach completely solves the balance problem.
The OTA needs to be moved forward in order to achieve good balance on the declination axis of the GP mount or the altitude axis of the altaz mount.
The solution is the Intes Sliding Bar Dovetail (listed as Mount Adapter Plate for Vixen). The base of the plate has two holes which align perfectly with the pair of ¼"-20 threaded holes in the base plate of the OTA. The Intes Sliding Bar is probably available from some U.S. dealers. I purchased mine from Marcus Ludes of APM for about $65.00. Worth every penny.
Deep Sky Objects (DSOs): For many DSOs, there is not a dramatic difference in the performance of these two instruments. The Newt does display some tiny diffraction spikes on stars from the 3 vane spider. The generous field of view afforded by the much faster Newt is, in some instances, preferable. Some Open Clusters are easier to pick out from rich star fields if they are nicely framed.
Lunar and Planetary Observation: The superior optics of the Argonaut really set it apart from the Newt on these targets. The Argonaut takes high power extremely well. Conditions permitting, the Argonaut delivers fine planetary images at 350x or more. The Newt is far from useless on planets, but it simply lacks the high contrast of the Argonaut. 200x seem to be the practical limit for the Newt.
Double Stars: Not much of a contest. The Argonaut has a very decided edge for double star work. Splitting some
of the tighter doubles requires high power and pinpoint images. The fast Newt is not nearly as competent for these
SkyView™ Deluxe 6" EQ Newtonian: A very nice choice for the potentially serious beginner. The overall operation is quite straightforward and the results rewarding. This system can provide many hours of enjoyable and productive observing. A good deal.
Argonaut™ 150mm Maksutov-Cassegrain: Probably not an ideal choice for beginners. This instrument does have some
eccentricities which beginners could find frustrating. The superior optics and quality of construction are impossible
to ignore. This is a rather sophisticated instrument at an extremely reasonable price.